In a patient who has had an acute myocardial infarction, when should beta‑blockers be started, what are the contraindications, preferred agents and dosing, and how long should therapy be continued?

Beta-Blocker Therapy Post-Myocardial Infarction

Oral beta-blockers should be started within the first 24 hours after MI in hemodynamically stable patients and continued indefinitely, with a minimum duration of 3 years for all patients and lifelong therapy for those with heart failure or LVEF <40%. 1

When to Start Beta-Blockers

Timing of Initiation

• Start oral beta-blockers within 24 hours of MI presentation in patients without contraindications 1
• Intravenous beta-blockers may be considered at presentation during primary PCI in patients without contraindications, no signs of acute heart failure, and systolic blood pressure >120 mmHg 1
• Treatment can be initiated as an inpatient or outpatient, but the patient must be hemodynamically stable with minimized fluid retention 2

Hemodynamic Requirements Before Starting

• Systolic blood pressure >120 mmHg (for IV administration) or stable blood pressure (for oral) 1
• No signs of acute heart failure (Killip class I) 1
• No evidence of low cardiac output state or risk for cardiogenic shock 1
• Heart rate adequate (not severe bradycardia <50 bpm) 1

Absolute Contraindications

Intravenous and oral beta-blockers must be avoided in the following situations: 1

• Hypotension or cardiogenic shock
• Acute heart failure with pulmonary congestion or low output signs
• High-grade atrioventricular block (second- or third-degree) without a pacemaker
• PR interval >0.24 seconds
• Severe bradycardia (<50 bpm)
• Active bronchospasm or severe asthma
• Right ventricular infarction

Important caveat: Patients with an initial contraindication should be reassessed after 24 hours, as many contraindications resolve with stabilization 1

Preferred Agents and Dosing

Evidence-Based Beta-Blockers

Only lipophilic beta-blockers (metoprolol, carvedilol, bisoprolol, propranolol, timolol) have demonstrated mortality reduction and prevention of sudden cardiac death post-MI 3. These agents show a 34% reduction in sudden cardiac death risk compared to placebo 3.

Metoprolol Dosing (Most Common Choice)

Immediate-release metoprolol tartrate: 4

• Acute phase (IV): Three 5 mg IV boluses at 2-minute intervals (total 15 mg), with continuous monitoring of blood pressure, heart rate, and ECG
• Transition to oral: Begin 50 mg orally every 6 hours, starting 15 minutes after the last IV dose, continued for 48 hours
• Maintenance: 100 mg orally twice daily thereafter
• For patients intolerant to full IV dose: Start 25-50 mg orally every 6 hours (depending on degree of intolerance) 15 minutes after last IV dose

Carvedilol Dosing (Alternative Agent)

Carvedilol must be taken with food to reduce orthostatic effects 2:

• Starting dose: 6.25 mg twice daily (or 3.125 mg twice daily if low blood pressure, heart rate, or fluid retention present)
• Up-titration: Increase to 12.5 mg twice daily after 3-10 days based on tolerability
• Target dose: 25 mg twice daily
• Titration pace: Can be slowed if clinically indicated; maintain on lower doses if higher doses not tolerated 2

Bisoprolol Dosing

• Acceptable alternative agent with similar efficacy 5, 6
• Specific dosing should follow standard post-MI protocols

Duration of Therapy

Minimum Duration for All Patients

Continue beta-blocker therapy for at least 3 years in all post-MI patients without contraindications 1, 7

Indefinite Therapy Indications (Class I Recommendation)

Beta-blockers must be continued indefinitely in: 1, 7

• All patients with heart failure symptoms
• All patients with LVEF <40%
• All patients with prior MI who have left ventricular dysfunction

Evidence for Duration

• The 2025 ACC/AHA guidelines recommend indefinite therapy for all post-MI patients unless contraindicated 1, 7
• Beta-blockers reduce mortality by 20-25% and reinfarction by similar magnitude over 2 years 8, 3
• The BETAMI-DANBLOCK trial (2025) demonstrated that beta-blockers reduce the composite endpoint of death or major adverse cardiovascular events (hazard ratio 0.85,95% CI 0.75-0.98, P=0.03) in patients with LVEF ≥40% 6

Recent Evidence Nuances

Preserved Ejection Fraction Controversy

The REDUCE-AMI trial (2024) found no benefit of beta-blockers in patients with LVEF ≥50% who underwent early coronary angiography (hazard ratio 0.96,95% CI 0.79-1.16, P=0.64) 5. However, the BETAMI-DANBLOCK trial (2025) showed significant benefit in patients with LVEF ≥40% (hazard ratio 0.85, P=0.03) 6.

Clinical interpretation: Despite the REDUCE-AMI findings, the 2025 ACC/AHA guidelines maintain a Class I recommendation for early beta-blocker initiation in all ACS patients without contraindications 1. The more recent BETAMI-DANBLOCK trial supports this recommendation and should guide practice 6.

Monitoring and Dose Adjustment

Parameters to Monitor

• Blood pressure and heart rate before each dose escalation 2, 4
• Signs of heart failure or fluid retention 2
• ECG for conduction abnormalities 4
• Standing systolic pressure 1 hour after dosing to assess orthostatic tolerance 2

When to Discontinue or Reduce Dose

• New or worsening heart failure symptoms 1
• Signs of cardiogenic shock 1
• Symptomatic bradycardia or hypotension 1
• Development of high-grade AV block 1

Special Populations

Hepatic Impairment

• Severe hepatic impairment: Carvedilol is contraindicated 2
• Any hepatic impairment: Metoprolol levels increase substantially; initiate at low doses with cautious gradual titration 4

Renal Impairment

• No dose adjustment required for metoprolol 4

Elderly Patients (>65 years)

• Use low initial starting doses with cautious titration 4
• Greater frequency of decreased hepatic, renal, or cardiac function requires careful monitoring 4

Common Pitfalls to Avoid

1. Do not withhold beta-blockers in stable patients based solely on older age or mild COPD without active bronchospasm 1
2. Do not use non-lipophilic beta-blockers (e.g., atenolol, nadolol) as they have not demonstrated sudden cardiac death reduction 3
3. Do not discontinue beta-blockers prematurely after hospital discharge; ensure indefinite continuation is clearly communicated 8, 9
4. Do not administer IV beta-blockers to patients with any signs of heart failure or hemodynamic instability 1
5. Do not forget to reassess patients with initial contraindications after 24 hours of stabilization 1